Bookmarks: Added BookmarksTree class that manages all bookmark's view types.
-BookmarksSidebar, BookmarksWidget,BookmarksManager and ... use BookmarksTree
-Added 'New Folder...'
-Fixed some issues
Bookmarks: Don't allow creating folder with translated name of "bookmarksToolbar", "bookmarksMenu" or "unsorted"!
Added 'Expand All' and 'Collapse All' buttons to bookmarks manager.
Serbian translation updates
Move connectons from .ui to .cpp
Bookmarks: when deleting lastFolder set it to default.
Add QupZilla* pointer to PopupWindow class
Updated German translation

Reviewed by J. Hooverman
Coding style
[Qt5] Ported all plugins to Qt5 plugin system
[Fix] Saving '+' character in passwords/usernames

Closes #703
RecoveryWidget: Switch positions of buttons.

Buttons now match Firefox.
Start new session is first and then Restore.
Fixed opening popup windows with QtWebKit 2.3

It now correctly opens new tab / popup window
according to arguments in window.open call.
File scheme handler: Sorting files case insensitive.
Fix possible crash on startup.

Don't calculate space for tab if the available
space is negative.
Ask user to allow site to use notifications/geolocation.

With option to remmber the choice for page.
Removed USE_QTWEBKIT_2_2 build variable.

It will now be automatically detected.
It assume that if you are building with Qt 4.8 and higher,
you have QtWebKit 2.2 and higher.
[Windows] fixed: open folder and select downloaded file (using ShellExecute for run explorer).
-Now it covers all possible situations (e.g. path with spaces, file without extention, ...)
Update .gitignore, ignoring manifest file.
[Windows] fixed include conflicting when defining 'W7TASKBAR'